Sextant



1,522,570 F. H. ALEXA NDER SEXTANT Filed Dec: 12, 1922 F. H. ALEXANDER SEXTANT Filed Dec, 12, 1922 4 Sheets-Sheet 2 Jan. 13., 1 925.

. 1,522,570 F. ALEXANDER SEXTANT Filed Dec: 12, 1922 4 Sheets-$heet s 1,522,570 F. H. ALEXANDER SEXTANT Filed Dec. 12, 1922 4 Sheets-Shee t 4 Patented Jan. 13, 1 25.

UNHT STATES FRANCIS HEB-BERT FRANCIS HERBERT SHIELDS, NORTH JIJI T all whom it may Be it known that PATENT OFFICE.

ENGLAND, ASSIGNOR TO SEX'IANT.

Application filed December 12, 1922.

concern I, FnANoIs HERBERT ALEXANDER, a subject of the King of Great Britain and Ireland,

residing at Jesinond,

Newcastle-on-Tyne, England, have invented Improvements in or of which the Relating to Sextants,

following is a specification.

This invention relates to sextants wherein use is made of an artificial horizon and it provide improved arrangements for enabling observations to be made with substanti and accuracy,

ally the same facility notwithstanding slight movements of the sextant, as when the natural or sea horizon is used The artificial horizon is constituted by a datum line which whilst it may alter in position with movement of the sextant, is so arranged that the path of the rays there from to the eye includes or passes closely adjacent to the oscillation axis of a long period pendulum clinometer.

found easier to ensure will be In this way it that the datum line image which appears shall per-- sist alongside the mirrored image of the celestial object under latter is brought observation when the down into the field of vision of the observer, and the usual con tact of images effected The datum line rays referred to may be diverted by a mirror the reflecting surface of which contains the oscillation axis of the pendulum and moves with datum line being optical elements; or the said through additional datum line rays may the latter, the

viewed indirectly be intercepted by the eye applied at or near the oscillation axis of the elinoineter pendu The clinometer may lum.

take various forms,

may have the means for viewing the datum line variously associated therewith and may in turn be incorporated in or combined with the sextant in sundry ways requirements any one of which in tion in one or The datum line to suit different and conditions, a variation in ay involve a modificamore of the others.

for the artificial horizon is formed upon some part of the movable element of the clinometer In the accompanying ferent arrangements tion are illustrated, Figs. 1

elevation and plan, sectional elevation an referred to.

drawings three difembodying the invenand 2 being an Figs. 3 and 4 a part d plan and Figs. 5 and Serial No. 606,477.

similar to Figs. 3, 4 and 5 of a second form of instrument. Fig. 10 is a part sectional elevation, Fig. 11 a plan also partly in sec-- tion and Fig. 12 an end elevation of an arrangement in which a olinometer and sextant separable one from the other are employed. Fig. 13 is a View similar to Fig. 10 showing the sextant removed. Fig. 14 1s a view similar to Fig. 11 illustrating a modification. 2

Referring first to Figs. 1 to 6, a sextant is employed part of theframe 1 of which extends into the wider portion 2 of a totally closed case, the narrower portion 3 of the case being set back as shown in Fig. 5 in order to exclude a portion of the sextant frame and enable the eye to be more readily applied to the telescope 4. The graduated are 6 is also external to the case 2, 3, the radius arm 7 which works over it and which carries the index glass 8 being cranked to clear the horizon glass comprising the part 9 reflecting the celestial object and the clear part 10 for observing thenatural horizon. 11 is the handle of the instrument upon which the case is mounted.

12 is a long period pendulum the spindle 13 of which is freely movable in bearings 14, within the case, 15 being a mirror mounted upon an extension of the spindle 13 so that its reflecting surface contains the axisof the pendulum. 16 is a double refleeting prism associated with the telescope 4 and mirror 15. The datum mark or line indicated at 17 may be marked upon or produced as by masking a translucent membrane carried by a bracket 18 from the pendulum 12. Behind said bracket an illuminant 19 is arranged for use in darkness, the datum line at other times being rendered visible by light admitted through a window 20 in the case. 21 is a collimating lens carried by a bracket 22 from the pendulum 12. Other portions of the cli'nometer, which form no part per se of the present invention but which are shown, comprise an auxiliary pendulum 23 suspended, in the case extension 24, coaxially with but independently of the pendulum 12, magnets 25 on the lat-terand magnets 26 on the pendulum 23. i

The disposition of the parts is such that the oscillation axis 01 the pendulum arrangement is located between the axis of the radius arm 7 and the graduated are 6.

As will be obvious minor modifications may be adopted it being permissible for example to employ in lieu of the prism 16 mirrors occupying the positions of the re fleeting surfaces of the latter.

A simplified instrument in which the datum mark is directly visible through the telescope 4 is that shown in Figs. 7, 8 and 9 where the pendulum case 2 is combined with an ordinary sextant having a horizon glass clear part 27 in which the datum mark appears alongside the reflection ot the celestial object in the horizon glass part 9. In this example the member constituting the datum mark 17 and the collimating lens 21 are carried by one and the same bracket 28 from the pendulum.

In the arrangement shown in Figs. 10 to 13 the sextant and the olinometer case are not directly connected together the intention being to enable the sextant to be removed and stored as usual leaving the olinometer in situ uponthe deck of a ship for example, which in view of the more delicate nature of its construction is more advantageous.

As here shown the sextant, wh'ch may be of any ordinary or usual form, except that it has an additional clear portion 29 in the horizon glass for use with the artificial horizon, is removably attached to a holder 30 as by inserting its supporting feet into the socketed lugs 31. 32 so positioned that when pivot coaxial with the axis of the olinometer pendulum, the telescope necessitates application of the eye at substantially the axis aforesaid. 33 is a handle by which the holder 30 is angularly adjusted about its pivotto keep the horizon datum line in view when necessary. The olinometer case 34 is shown as cylindrical in shape with 2 seg mental side extension 35 to accommodate a pendulum bracket 28 which in this instance carries not only the colhmating lens 21, and the datum mark 17 but also the illumimounted upon a nant 19.

For the purpose of supporting the clinometer, the case 34 may be attached as shown to a shaft 36rotatable, as by a handle 37, within a sleeve 38 supported from a pedestal 39 by a fitting 40. The sleeve 38 is adj ustable as to height in said fitting bymeans of a clamping collar 41 under the control of a handled set screw 42.

In some cases it may be desired to employ a sextant the horizon glass of which is in no way altered. This can bedone by re- .ducing the width of the case extension 35 as shown in Fig. 14 so that it does not overlap the index glass 8, and attaching to the holder 30 a periscope 43 comprising prisms Th s holder has a lug said olinometer and 44 or mirrors whereby the image of the datum mark 17 is so reflected that it can be seen by the observer at the telescope through the glass 11 ordinarily adapted for viewing the natural horizon. I

From these examples other modifications will be readily ascertainable without specific direction.

IV hat I claim is 1. The combination, with a sextant, having an eye-piece, of a support, a olinometer having a long period pendulum and a member movable with said pendulum having a single datum mark serving as an artificial horizon, the sextant and olinometer being arranged on said support insuch a manner that the oscillationaxis of the pendulum is located between the datum mark and sex taut eyepiece closely adjacent to the path of the observed rays from the datum mark, substantially as described.

2. The combination, with a sextant, having an eyepiece, of a support, a clinometer having a long period pendulum and a member movable with said pendulum having a single datum horizon, the sextant and olinometer being arranged on said support in such a manner that the oscillation axis of the pendulum is located between the datum mark'and sextant eye piece and in the rays from the datum mark, substantially as described. 2 V

3. In combination, a support, a olinometer having a long period pendulum, carrying a single datum mark serving as an artificial horizon and a sextant having a telescope, sextant being arranged on said support in such a manner that the oscillation axis of the pendulum is located in the path of the observed rays proceeding from the datum mark to the telescope, with the eye piece of the telescope substantially at such centre of oscillation, substantially as described.

4. In combination, a pendulum olinometer having an, artificial horizon and comprising a casing, a support for stationarily holding said casing, a sextant for use with theclinometer aforesaid and means whereby the sextant can be attached to and removed from the olinometer casing, the latter being adapted to remain at all times-upon its support, substantially as described.

5. In combination, a pendulum olinometer having an artificial horizon and comprising a casing, a support for stationarily holding said casing, a sextant for use with the clinometer aforesaid and means whereby the sextant can be temporarily attached to the olinometer casingand bodily adjusted thereon whilst in use.

6. In combination, a pendulum'clinometer having an artificial horizon and comprising a casing, a support upon which thecasing mark serving as an artificial path of the observed" lUU Iii

can be adjusted as to position and adapted to stationarily hold the same, a sextant for use with the clinometer aforesaid and means whereby the sextant can be attached to and removed from the clinometer casing, the latter being adapted to remain at all times upon its support, substantially as described.

7. In combination, a pendulum clinometer having an artificial horizon and comprising a casing, a pedestal, means adapted to stationarily support the casing upon the pedestal, means whereby the height of casing can be adiusted, a sextant for use with the clinonieter aforesaid and means whereby th sextant can be temporarily attached to the clinometer and bodily adjusted thereon whilst in use.

8. In combination, a pendulum clinometer having an artificial horizon and comprising a casing, a pedestal, means adapted to stationarily support the casing upon the pedestal, means whereby the height of casing can be adjusted, means whereby the same can be angularly adjusted about a vertical axis, a sextant for use with the clinometer atoresaid and means whereby the sextant can be temporarily attached to the clinometer and bodily adjusted thereon whilst in use.

9. In combination, a clinometer comprising a casing and a long period pendulum movable about a horizontal axis, asextant, a holder for said sextant having a pivot substantially coincident with the oscillation axis of the pendulum and means for adjusting the holder about the axis aforesaid.

10. In combination, a clinometer comprising a casing and a long period pendulum movable about a horizontal axis, a sextant having a telescope, a holder for said sextant having a pivot substantially coincident with the oscillation axis of the pendulum, means tor temporarily attaching the sextant to the holder, such attachment resulting in the eye piece of the telescope being substantially alongside the oscillation axis of the clinometer, and means for adjusting the holder about said axis.

11. In combination, a clinometer comprising a casing and a long period pendulum movable therein about a horizontal axis, such pendulum carrying a single datum marki a sextant having a telescope, an external holder for said sextant having a pivot substantially coincident with the oscillation axis of the pendulum and periscopic means whereby rays from the datum mark upon the pendulum within the casing are first diverted in a direction parallel to the oscilla tion axis of the pendulum and thereafter at right angles to such direction to be viewed by the telescope.

Signed at South Shields, in the county of Durham, this eighth day of November. 1922.

FRANCIS HERBERT ALEXANDER. 

